The present invention relates to a method for coiling a rolled metal strip, in particular a steel strip,                wherein the metal strip is deflected by a drive roller unit from a first transportation direction to a second transportation direction and is fed to a coiler;        wherein the metal strip in the coiler is coiled to form a coil having a coil diameter;        wherein a plastic deformation of an end portion of the metal strip is caused such that the end portion in the uninfluenced state is curved at a radius of curvature;        wherein the plastic deformation of the end portion is at least partially caused by an asymmetric impingement on the sides of the end portion with a cooling medium prior to and/or during the coiling of the end portion.        
The present invention furthermore relates to a coiling installation for coiling a rolled metal strip, in particular a steel strip,                wherein the coiling installation has a drive roller unit which deflects the metal strip from a first transportation direction to a second transportation direction;        wherein the coiling installation has a coiler to which the metal strip is fed from the drive roller unit in the second transportation direction and in which the metal strip is coiled so as to form a coil having a coil diameter;        wherein the coiling installation has a deformation installation which causes a plastic deformation of an end portion of the metal strip such that the end portion in the uninfluenced state is curved at a curvature radius;        wherein the deformation installation is configured as a cooling installation which impinges on the end portion with a cooling medium prior to and/or during the coiling of the end portion.        
In hot-rolling lines, after the final rolling pass, a metal strip, usually a steel strip, is typically initially cooled to a predefined temperature (coiling temperature) in a cooling section. Thereafter, the cooled strip is coiled to form a coil. It is possible for the coiling temperature to be constant, when viewed along the length of the metal strip. Alternatively, when viewed along the length of the metal strip, it is possible for the coiling temperature to be variable. For example, the strip head (i.e. the front end of the strip) and the strip tail (i.e. the rear end of the strip) can be coiled when not cooled. The coiled coil is subsequently secured for storage and for transportation against any self-acting unwinding or opening. For this purpose, the coil is typically removed from the coiler by a transportation device and fed to a strapping machine. Securing is performed in the strapping machine. Prior to being pulled from the coiling mandrel, the coiled coil is rotated such that the end of the strip projects only slightly beyond the lowermost point of the coil, and the coil is thus stabilized by its own weight.
A plastic deformation of the metal strip typically arises already during the coiling of the metal strip so as to form the coil. Nevertheless, spontaneous opening or unrolling, respectively, of an as yet unsecured coil can arise in many cases. The reason this lies in elastic residual stresses in the coilings of the coiled coil. The degree of these residual stresses depends on several factors, for example on the thickness of the strip and on the flow stress at the coiling temperature. Spontaneous opening or unrolling, respectively, of this type can arise particularly in the case of high-tensile products having a flow stress of approx. 500 MPa (or more) and a thickness of approx. 12 mm (or more).
It is known from WO 2008/000 348 A1 for the end portion of the metal strip to be pre-bent by means of a straightening unit. According to WO 2008/000 348 A1, the combination of a bottom roller and of a top roller of the drive roller unit, in addition to a downholding roller that is upstream of the drive roller unit and is capable of being placed on the metal strip, can be used as the straightening unit. Alternatively, a straightening unit that is upstream or downstream of the drive roller unit can be used as the straightening unit. The upstream or downstream straightening unit comprises in each case three sequentially disposed straightening rollers that are placed in alternating manner on the one and on the other side of the metal strip, wherein in each case at least one of the straightening rollers being capable of being placed on the metal strip.
It is known from EP 0 906 797 A1 for a stretch leveler having a plurality of worker rollers to be disposed between the drive roller unit and the coiler, so that the metal strip is deflected on each worker roller. Cooling of the metal strip can additionally be performed between the worker rollers. A distribution of stress in the metal strip across the width of the strip can be influenced in particular by means of the assembly of EP 0 906 797 A1.
A method and a coiling installation of the type mentioned at the outset are known from WO 2011/073 016 A1. In WO 2011/073 016 A1, the end portion is cooled directly prior to coiling. The length of the end portion is chosen such that the latter is between one and five coilings.
A method and a coiling installation of the type mentioned at the outset are likewise known from JP 2012 024 793 A. In the case of JP 2012 024 793 A, the coil is first completely coiled. The outermost coiling of the coil is then cooled. The coil is rotated during cooling.
An equivalent disclosed content can be derived from JP 2010 162 594 A.